As is known, there are a variety of systems for monitoring and controlling manufacturing processes, inventory systems, emergency control systems, and the like. Most automated systems use remote sensors and controllers to monitor and respond to various system parameters to reach desired results. A number of control systems utilize computers or dedicated microprocessors in association with appropriate software to process system inputs, model system responses, and control actuators to implement corrections within a system.
One way to classify control systems is by the timing involved between subsequent monitoring occurrences. Control systems can be classified as aperiodic or random, periodic, and real-time. A number of remotely distributed service industries implement the monitoring and controlling process steps through manual inspection and intervention.
Aperiodic manual monitoring systems (those that do not operate on a predetermined cycle) are inherently inefficient as they require a service technician to physically traverse an area to record data, repair out of order equipment, add inventory to a vending machine, and the like. Such service trips are carried out in a number of industries with the associated costs being transferred to the consumers of the service.
Conversely, utility meter monitoring, recording, and client billing are un representative of discrete steps in a periodic monitoring system. In the past, utility providers sent a technician from meter to meter on a periodic basis to verify meter operation and to record utility use. One method of cutting utility meter reading operating expenses involved increasing the period at which manual monitoring and meter data recording was performed. While this modified method decreased the monitoring and recording expense associated with more frequent meter observation and was convenient for consumers who favor the consistent billed amounts associated with “budget billing,” the utility provider retained the costs associated with less frequent meter readings and the processing costs associated with reconciling consumer accounts.
Lastly, a number of environmental and safety systems require constant or real-time monitoring. Heating, ventilation, and air-conditioning (HVAC) systems, fire reporting and damage control systems, alarm systems, and access control systems are representative systems that utilize real-time monitoring and often require immediate feedback and control. These real-time systems have been the target of control system theory and application for some time.
Home automation systems may comprise control systems that exemplify all three periodicity variations. For example, a remote command designed to turn on interior lights may be classified as aperiodic or random. Whereas, it may be desirable to send periodic control signals to a landscape lighting system, pet feeders, irrigation systems, etc. Finally, security systems, smoke detectors, and related fire prevention systems exemplify household systems in need of real-time monitoring and control.
Various schemes have been proposed to facilitate inter-device communications between closely located devices, including radio-frequency (RF) transmission, light transmission (including infra-red), and control signal modulation over the local power distribution network. For example, U.S. Pat. No. 4,697,166 to Warnagiris et al. describes a power-line carrier backbone for inter-element communications. As recognized in U.S. Pat. No. 5,471,190 to Zimmerman, there is a growing interest in home automation systems and products that facilitate such systems. One system, critically described in the Zimmerman patent, is the X-10 system. Recognizing that consumers will soon demand interoperability between household systems, appliances, and computing devices, the Electronics Industry Association (EIA) has adopted an industry standard, known as the Consumer Electronics Bus (CEBus). The CEBus is designed to provide reliable communications between suitably configured residential devices through a multi-transmission media approach within a single residence.
One problem with expanding the use of control systems technology to distributed systems is the cost associated with the necessary build-out of the local sensor-actuator infrastructure necessary to interconnect the various devices. A typical approach to implementing control system technology is to install a local network of hard-wired sensors and actuators along with a local controller. Not only is there expense associated with developing and installing appropriate sensors and actuators but the added expense of connecting functional sensors and actuators with the local controller. Another prohibitive cost associated with applying control systems technology to distributed systems is the installation and operational expense associated with programming the local controller.
Accordingly, an alternative solution for implementing a distributed control system suitable for home automation that overcomes the shortcomings of the prior art is desired.